Analysis: Light mix of precip Monday night

By
Jason Samenow

UPDATE, 10:55 p.m. Sunday night: Latest model guidance (the NAM and GFS) suggests the possibility of a coating to an inch or so of snow Monday evening between about 7 p.m. and midnight before precip changes to sleet and freezing rain. The models simulate heavier precipitation after midnight compared to this morning's run, but also warmer air which would allow for the ice to change to rain before Tuesday's a.m. commute except for outlying north and west suburbs. We'll have more tomorrow morning.

From earlier (1:25 p.m.): A complex weather scenario sets up Monday, providing the metro region with a good possibility of mixed precipitation Monday night through Tuesday morning. This does not look like a major storm, but may result in slippery travel Tuesday morning, especially west of I-95.

Precipitation may (40% chance) begin as a brief period of light snow between 7 p.m. and 10 p.m. Monday night, before changing to sleet from southeast to northwest after midnight. By the morning commute Tuesday, precipitation may change to plain rain east of I-95 with the possibility of freezing rain increasing as you head north and west of I-95. Precipitation cuts off mid-to-late Tuesday morning and temperatures rise above freezing everywhere.

Although precipitation amounts are likely to be on the light side, it doesn't take much freezing rain to cause significant issues on the roads.

TECHNICAL DISCUSSION

Surface map forecast for 7 a.m. Tuesday morning. One area of low pressure is heading through the Great Lakes, while a second develops over eastern North Carolina. High pressure is retreating to offshore the Northeast. Source: NOAA.

One area of low pressure is forecast to head up through the Great Lakes as high pressure over the northeast U.S. moves offshore. As Wes discussed Friday, that's not a good setup for snow. We usually need high pressure anchored to the north and northwest to supply cold air for snow over our region and, in this case, the source of cold air is moving away.

The complicating factor this time around is that a second area of low pressure will form to the south over eastern North Carolina and track to our east. The flow around that developing low should help keep flow coming from the north even as our source of cold air moves away. Thus, the stale cold air that's in place Monday will be slow to erode Monday night and Tuesday as long as winds remain from the north.

So we'll have some marginally cold air in place Monday night into early Tuesday but how much moisture are we talking about? It depends. The low headed up through the Great Lakes will be too far away to produce precipitation over our region (and doesn't merge/phase with the storm to the south until the storm to the south off the coast of New England). So our precipitation will originate from the low developing to our southeast.

However, the NAM model tracks the southeast low far enough off the coast to only give us some very light precipitation. The GFS had simulated a fair amount of precipitation for us from this low, but has backed off somewhat in recent runs. The latest Euro model is pretty consistent with the GFS. Liquid equivalent precipitation amounts vary from as little as just a few hundredths of an inch in the NAM model to 0.2-0.3" in the GFS and Euro. So precipitation amounts are either likely to be light or very light. (A westward shift in the low could increase amounts to moderate, but probably would increase the amount of warm air and rain)

As just a little frozen precipitation, especially ice, can cause significant problems, the question becomes, how does the precipitation evolve? Will it change to rain and melt and when? Will there by any snow?

If we can get some precipitation in here early enough Monday night, the atmosphere would probably be cold enough for the precipitation to start as snow. The GFS model suggests a dusting to an inch of snow before any changeover, whereas the NAM and Euro indicate little to no snow.

After midnight, from southeast to northwest, a warm pocket around 5,000 feet works its way in, so any snow would probably mix with and change to sleet. Then, into the predawn hours, enough warm air should arrive aloft to change the sleet to freezing rain.

What happens for the morning commute?

GFS model simulation valid 7 a.m. Tuesday morning. About 0.1-0.25" of mixed precipitation has accumulated in the last six hours. The freezing line extends from eastern Loudoun county through northwest Montgomery county. Source: StormVistaWxModels.com

By 7 a.m. or so, the freezing line should be somewhere in the vicinity of the metro region but it's difficult pinpoint exactly where it will be. The GFS model simulates it cutting through eastern Loudoun county and northwest Montgomery county, whereas the NAM model - which has higher resolution - places it just east of the District. So there's the possibility of light freezing rain and freezing drizzle in the metro region for the morning commute Tuesday.

As the morning wears on, all models warm the surface above freezing from southeast to northwest. After 10 a.m. or so, any lingering precipitation (doesn't look like much) should fall in the form of plain rain and any ice would melt.

The bottom line is that models suggest light to very light amounts of precipitation, but enough cold air may stick around for a frozen mix Monday night into Tuesday morning, especially north and west of the District.

Snow late week?

Both the GFS and the Euro model show potential for a winter storm late next week - Friday or Saturday. However, it's not clear whether the storm will be suppressed to the south and east, or come up the coast. If a storm tracks close enough to impact us, this time cold high pressure lurks to the north and northwest, so there's better potential for snow than with the event Monday night into Tuesday.

I am in Chicago as I write this and let me tell you it is awesome. Fluffy flakes floating to the ground. About 20 degrees and 6 inches of snow on the ground. I wish I could bring this back to DC with me!

Once again, if it's not going to snow; I'd rather it rain. Why? Because freezing rain/sleet/ice/mix are the four things I detest when it comes to D.C. weather.

I think that this city can recover from a 12 inch blizzard better than it can from a 1/2" sheet of ice. Remember a few years ago when the Springfield mixing bowl was shut down for hours? That was a freezing rain event, I believe.

I can't recall ever meeting someone who looks forward to ice storms or sleet. All it does is cause endless problems.

The good thing about this storm is that the models are trending toward lighter precip amounts. Considering that most of this storm will be rain anyway, I don't think there will be too many problems.

I'm still very hopeful that the late-week system turns into something. As I said before: Bring on the SNOW!!!!! Feet and feet of SNOW!!!!! I am probably the biggest snowlover on this blog. I have been for many, many years; ever since I was a little kid.

The reason that I'm hopeful for the late-week is because it is now showing up on both the GFS and the Euro. The NAM doesn't go out that far, but I hope it comes aboard once we get closer to the *potential* event.

It appears that there will be plenty of cold air in place for this one as well. My only concern is the dreaded out to sea scenario that could play out.

If the GFS verifies, that would be the case: out to sea. But if the Euro verifies; well that's a whole different story. I'm just really disappointed that we haven't seen a single snowfall this year that has completely covered the grass. Every time, it's the same thing: out to sea and/or too develops too far north.

If anyone in NYC, Philly, or Boston is reading this, please, please, please, I beg of you, send us some snow! We're desperate down here!

The snowpocalypse and snowmageddon spoiled us all. I remember last February thinking of 6" as nothing. Now, 6" would seem like a godsend. My shovels are just sitting there in the garage, waiting to be used.

Last winter, I was lucky enough to be able to borrow my neighbor's snowblower, because quite frankly, 30"+ is waaay to much to shovel. You could really hurt your back doing that. And my driveway is pretty long, too.

I don't even want to watch the football game in Chicago. That would put me into "snow withdrawal" :)

By the way, it looks like we could be in for some ultra-cold weather by next weekend with highs in the low-mid 20s and lows in the lower teens downtown.

It looks to me that the most dangerous period for commuters is to those who normally get an early start between 4-7 AM. SREF probabilities for freezing raid are up to 50% during this period and do not fall to near zero until mid to late morning.

One expects that at least main roads will be treated. Non-treated road surfaces can be extremely treacherous. I've documented cases in the past where even less than .01" of rain freezing on roads can be deadly.

@bobmiller2-- The event you refer to @ the Mixing Bowl in Feb 08 was a freezing rain event. My husband was one of the unlucky folks stuck on I-395 for over 5 hours. I had someone drive me home that night (as I got a nasty sinus headache that day at work and could hardly focus on driving), so I ended up having to borrow a carseat from one neighbor and ask another neighbor to take me to my son's daycare when it became clear hubby wasn't getting home anytime soon. A nightmare. He got home at 10:30 pm. Caught the DC mets by surprise, and VDOT as well (to say the least). I think that's why you see the roads white with road salt now every time we get a forecast for wintry precip. Just my opinion.

I for one will be watching the forecast for Tues AM, as I'm not convinced the warm air is gonna come in around DC metro (and eastern Prince William County to be exact) as fast as being predicted. Nothing scientific to base that on, just gut feeling. Rt 1 and I-95 become skating rinks in a hurry.

Everyone be safe, and stay informed. Two of the best things you can do for yourself and for your family. :)

I wonder what impact this will have on moco schools. Delay seems definite... im even thinking closure. Areas like clarksburg and poolsville should have freezing rain until 9am or so, no? This will mess up midterm exams, but im not complaining.

@bobmiller2--Forgot to add-- you were SO lucky to have the snowblower last year! Guess who had to shovel the driveway here in Dumfries? Yep, me, myself, and I. southbridgedad broke his ankle on Feb 1st. If anything good came from it, I found out what I could REALLY do, and the CWG kept me one step ahead with forecasts!

I remember the ice storm that closed the mixing bowl well. I wasn't in the mixing bowl, but I was out in Reston trying to make my way back to Lake Ridge. I'd been watch the news all day and they kept saying "just rain - temps will go up to 35 once it starts" and that had been the trend all that winter - 33 degrees and rain. So I believed the forecast and headed out to a dr appointment in Reston. Only thing, it didn't warm up. It got colder. By the time I got home it was 28 degrees and still raining. Caught everyone off guard. And it hit right at rush hour. I don't think Tuesday AM will be like that.

@southbridgemom
I remember that storm as well. Wasn't at the mixing bowl, but when driving on a hilly road in Fairfax got into an accident because a car came spinning right at me. Wasn't too bad, at least the airbags didn't go off, but it sure was scary. And a few minutes after that another car slammed into into the other side of the road.
@BobMiller2
I hope we don't have a snowstorm that weekend. I'm a snowlover but I'm going to Florida that weekend to get away from the wind and cold. I don't want to miss all the fun!

General note: Please limit the discussion to the Mon night/Tues threat and potential for Fri/Sat. Discussion of storms being shown on models more than a week out (i.e. for 1/29)are a distraction. I'd prefer we not discuss GFS model output beyond 6 or 7 days.. the model has little to no skill/credibility much beyond that range. Also, I'd like to ask folks to be careful about "overcommenting". We appreciate everyone's participation and enthusiasm, but diversity and a mix of perspectives is good, rather than having a comment thread dominated by one or two people. So err on the side of making your point(s) in a fewer comments rather than more. Thanks.

Sorry if I'm the "overcommenter" you're referring to. I promise, I'm not trying to be disruptive; I just get a bit excited when it comes to winter weather. Once again, I'm sorry if what I said bothers you. I'm going to try to put several comments into one comment from now on.

@cubscapsfan

I wouldn't worry about missing a biggie. As Jason said, the GFS past 6 - 7 days has no skill.

@southbridgemom

Yeah, it was nice to have the snowblower. I can't believe you had to do all the shoveling without your husband's help!

@mamory1975

Yes, the mixing bowl disaster was pretty bad. I was lucky enough to be home that day, so I didn't experience it firsthand.

Light wind on Mon. heading 2 the 301 Bridge, hopefully the stripers will b biting.
Looks like the usual snow/sleet/rain scenerio that's is tpyical for this area. We all got 2 spoiled last winter.
Go Steelers.

VaTechBob - have a good time fishing. Glad the weather will be okay for you, and hope the fish do indeed bite for you. Last winter was too "easy" and we did get spoiled. Agree. The more typical--and difficult to forecast--scenarios appear more in the cards this winter as compared to last. However I am not discounting one moderate storm for the winter to give us snow--but it just isn't in the same phase that was too perfect for DC last year!

@frontieradjust--I was thinking the same thing. With bitter cold air over New England tomorrow, it looks like a classic setup for cold air damming east of the Appalachians.

CWG: Since the GFS is sometimes known to erode surface cold air too quickly east of the mountains, how do you correct for that in your forecast? Seems like cold air damming situations always creep up on us unexpectedly in this area.

BobMiller2 - with all due respect, if you've been waiting THAT breathlessly for this update to come out, you seriously need to either A) spend some more quality time with your family, or B) consider taking up some additional hobbies to get you out from behind the computer monitor more often.

And Jason makes a wonderful point: please DO think before submitting the MYRIAD of comments and one-liners (complete with annoying smileys) containing so much needless background noise, e.g., getting folks whipped up into a frenzy over fantasy storms on the GFS 10 days out (and then not being able to discuss the models when folks ask you pointed questions), or glibly suggesting non-snowlovers "move to Florida, or Africa." Seriously, man??

Honestly, you increasingly dominate nearly every post on CWG with your comments so much lately and seriously degrade the signal-to-noise ratio, that I almost hate to check into CWG for the detailed articles. Don't mean this as an attack, but you REALLY need to dial it back a couple of notches.

I don't know about the rest of you, but I PINE for the days back when CWG was a privately hosted blog that was a labor of love of Jason & The Gang, and not some big corporate-y, sellout-ish subsite of the abhorrent Washington Post. I'm sure it's all about the hits and the traffic throughput now, but back then, it was a cozy, core group of repeat commenters that felt far more like a family than the WaPo version of this blog ever has. Just sayin'...rant closed.

Well I for one love this blog! I have learned so much and have a real passion for the weather and now a little more knowledge to go along with the passion. One person's cozy, core group of repeat commenters is another's annoying overposting.

In any case, back to the topic at hand. Thanks CWG for your spot on analysis last week. I am watching closely for this week as I fly back in from warmer climes. I am hoping the icing is not too bad! Those storms are the worst!

I have PLENTY of hobbies, believe me. Most of the comments I post aren't even posted from my computer; they're posted from my phone while I'm out and about. so don't get the impression that I'm some guy who hangs out in front of the computer all day. I really don't appreciate people like you who personally attack me and the other commenters.

And in case you haven't noticed, my comments are always weather related, unlike some other people on here.

@tobeblut, I have followed this blog since the old days and i disagree with you 100% about CWG being a sellout and corporate. I think the analysis is still great and the new members like Wes to explain everything about snow are a great addition to the team. Unlike accuweather, which does produce and exaggerated snow for the website hits, CWG keeps it real and says how it is. In addition, It's great that they can answer commenter's questions. Keep up the good work guys! and about @tobeblunt, Haters gonna hate.

Well, samdman95, I never once denigrated the forecasting skills of the CWG folks, or compared them to SemiAccuWeather, now did I? Thanks, though, for totally taking my comments out of context.

CWG's forecasting is as spot-on (or as close to that special place that it can be in this area) as it was in the old days. And there are plenty of nice pluses in the WaPo version of this blog, the presence of Wes Junker's expertise certainly being one of them, and a general expansion of the team.

Folks love to toss around that term, "keeping it real" - well, welcome to my world. Having one person dominate the conversation most of the time can have the effect of intimidating lots of others who'd like to wade in with their own questions or observations. God knows I witness that every day at work as a project manager overseeing a team of several dozen people.

And BobMiller2, I truly don't mean to attack, but sometimes the truth hurts. On this blog, you're often the moral equivalent of the initial commenter who screams, "FIRST!" as soon as a new post goes up. Your posts might be PRIMARILY weather-related (not always, nice try), they are OFTEN wrapped around some Fantasyland storm that's dozens of days out on some model, peppered with inane questions to Jason & The Gang about whether the phantom storm will come to fruition. Here's a fresh idea - how about sticking as close as possible to the subject of the post you're commenting on?

MONDAY NIGHT...SNOW AND SLEET IN THE EVENING...THEN FREEZING RAIN AFTER MIDNIGHT. SNOW AND SLEET ACCUMULATION AROUND AN INCH. ICE ACCUMULATION AROUND A TENTH OF AN INCH. LOWS IN THE UPPER 20S. EAST WINDS AROUND 5 MPH. CHANCE OF PRECIPITATION 90 PERCENT.

CWG-
It is really important to get the word out that getting into a car early Tuesday morning may be very dangerous.
This is the most important task of meterologists -- to keep us safe when we have this kind of precipitation event.
I live in Western Loudoun and will surely be keeping track of the type of precipitation and timing.

ACCuweather is posting 3 storms in the next week haha, the one tmrw is forcasted to bring .4 in ice, CWG is considered very dangerous
Then there's the storm thursnight-fri that has 6inches snow
then the storm next sunday bringing 2 inches snow

I'm all for snow but could there be any way this forcasting stuff could be made easier
Just hypothesis

Since this thread has gone from generally a blog about the storm Monday?Tuesday to a general discussion about the blog itself, let me comment.
The CWG website of old was different in that it WAS a family. Yeah, we were a bit selfish in that it was known to a local few and we had it all to ourselves. Anyone remember the talk of contrails as a conspiracy to control the weather? Do I wish it were that small community all over again? Well... maybe. But I do enjoy all of our new siblings in the new CWG family.

But time moves on and so do we. The "new" CWG at the Washington Post IS different. The coverage is better. The team has grown and added people to expand the areas of expertise. What has remained the same is the forecasting of our weather. That's what it boils down to. Te best forecast money can buy. They still explain in detail and in a language we can all understand what the darn weather is going to be like in the next few days. And when they are wrong, they admit it and explain why! And on top of that, they answer all of our questions in a timely manner without the condescending attitude one might find when a novice is talking to an expert.

So in departing I would like to say thank you to the staff at CWG for all you do for us weather weenies. All of the BobMiller2's, tone it down but don't stop. You are an integral part of the family. Mon/Tue looks to be a bit tricky but not too bad and the late week storm is... well... a late week maybe.

Till we meet again.

PS Since this took so long to write and then post I hope it makes it in time before the next thread throws it into oblivion.

went skating on lake barcroft today. i can't believe i'm saying this, but we need rain. the surface was as bad as i've ever skated. it's been frozen ever since dec 13th or so. and has "withstood" a few teeny-tiny .5" storms or whatever. all that snow has now melted and refrozen to create a mosaic of smooth and bumpy parts. after all the dustings and people skating on the best parts... it's done... 1/2" rain then some cold air would be like a zamboni....

all that is said from the perspective of a skater person. really, i'd just like to have snow, snow, snow. but apparently that's not gonna happen mon/tue, so i'll order a rain zamboni for monday, then cold temps and snow next weekend.

@Jason and all of the CWG: Your blog is not a sellout! Thank you so much for the detailed discussion of the Tuesday morning commute. I am one of the early commuters Steve-T refers to; I'll take the bus on Tuesday if I have to go.

And I'll add that I'm far more bothered by those whose comments complain about the quantity or quality of others' posts than I could ever be by those who comment enthusiastically here. I know how to scan and scroll if I don't want to read certain posts.

any chance CWG can make a precip map of the green, pink and white and its timing like the local news does?... im just to the east of DC in Hyattsville and im just really wanting to see the timing of each precip type from when it starts to when it changes each time.

do you think this front end snow will be a plowable event?

do you think there will be enough ice accum to warrant salting or will it turn to rain before too much build up?

what are the odds the warm air comes in earlier than forecasted, like say around midnight and turns everything to rain, especially east of DC around my area?

The 00 NAM looks a bit colder aloft to me for the far western suburbs when I compare the 18z 42 hr view to the 00z 36 hr view... wondering if I could see snow into Tuesday morning out in the Blue Ridge Mtns...

@Camden-- agreed. Tuesday to be interesting, to say the least. I'll be waiting on Tuesday PM to see what the long range models show for the weekend, as I have scheduled my Dreamdinners appt for Saturday AM. Also scheduled a long overdue visit after that with my friend and her kids. Will be thinking of a 'plan b' for Saturday in the meantime.

@BobMiller2-- My 17 y/o daughter and 7 y/o son helped me w/shoveling for snow #1. When it stopped, 2 girlfriends came and helped me dig out the basement steps. After snow #2 a neighbor across the street (who found out my plight) helped me dig out the driveway where the plows blocked us in. Otherwise, it was all 'girl power'. :) When it gets tough you find out what you can REALLY do.

@Camden-- agreed. Tuesday will be interesting, to say the least. I'll be waiting on Tuesday PM to see what the long range models show for the weekend, as I have scheduled my Dreamdinners appt for Saturday AM. Also scheduled a long overdue visit after that with my friend and her kids. Will be thinking of a 'plan b' for Saturday in the meantime.

@BobMiller2-- My 17 y/o daughter and 7 y/o son helped me w/shoveling for snow #1. When it stopped, 2 girlfriends came and helped me dig out the basement steps. After snow #2 a neighbor across the street (who found out my plight) helped me dig out the driveway where the plows blocked us in. Otherwise, it was all 'girl power'. :) When it gets tough you find out what you can REALLY do.

Folks-Some good discussion tonight and thanks for the all of the feedback. Let's just all remember to remain civil...that's been one of the best things about this forum over the years. Time for me to look at the 0z models...

Did anyone see the movie Ice Storm? It had some beautiful shots of what an ice storm looks like, and the storm setting was analogous for the bleak, fragile, and dangerous things going on in the characters' lives. I always wanted to experience the beauty of such an event, but of course I worry about the dangers of ice.

Reading over the late NWS discussion from tonight, sounds to me like they're pretty confident that the high over New England will move off-shore Monday night, and not cause extensive cold air damming as frontieradjust and I were wondering about earlier. I assume this is because the winds would then turn more easterly? We shall see...

I just added an update to the beginning of this post. Reload your browsers to read. Models have come in wetter and warmer...that might mean more snow on the front end, and less ice on the tail end (coinciding with Tuesday morning's commute)- a good thing.

Walter, I grew up in Vienna in the mid 50's, got married in 70, & lived in NOVA until 79, now in Spotsy. I used to ice skate every winter from the late 50's-early 70's on local ponds. Then skated on the Occoquan thru the mid -late 80's, I was the manager at Fountainhead so I had access to the res. in the winter. Nothing made the ice smoother than a little rain on the ice. Seems like since the late 80's the ice would never get thick enough to skate on, except for a short period of time every few winters. Wonder if u noticed the same thing in regards 2 the ice. In Jan 77 the ice on the Occoquan was 17" thick.

VaTechBob,
i remember winters in the late 70s and early 80s when the entire lake would freeze. that's never happened since then except for one year in the early 90s where almost the whole thing froze.

but... these last few years we have had the lake frozen enough to skate on for a week or so just about every winter. this winter has been extraordinary in that it's been skate-able for over a month! and i don't recall that ever having happened. (of course for that to happen you can't have a big snow, and we've had lots of cold and no big snows, so it's been just the right conditions.)

but now the surface is pretty seriously roughed up. in that regard a good rain-zamboni might be just what the doctor ordered.